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The Seattle Times
Copyright © The Seattle Times Company
Eating by blood type
New diet book hypothesizes that what we eat should
be governed by what our ancestors ate
by Mary Elizabeth Cronin
Seattle Times staff reporter
Is this just another diet fad?
No, says naturopathic physician Peter J. D'Adamo. His diet is no fad. It's actually thousands of years old. According to his research, if your ancestors hunted the American plains or the African savannah and ate meat, then you should. (Eat meat, that is; how you get the meat is your decision.) If instead they harvested grains and legumes in Europe or China, then yours should be a mainly vegetarian diet.
The reason he says you should eat the way your ancestors did is that your body has evolved to best digest and distribute the nutrients in those particular foods. And it doesn't matter whether you were adopted, don't know your family history or are estranged from your relatives because all you need to know about your gastrointestinal ancestry is in your blood type.
That's right: blood type.
D'Adamo's theories were recently published in an intriguing nutrition and diet book, "Eat Right For Your Blood Type: The Individualized Diet Solution to Staying Healthy, Living Longer and Achieving Your Ideal Weight," co-written with Catherine Whitney (Putnam, $22.95).
D'Adamo has spent more than 10 years researching the relationship between blood type and diet first postulated by his father, also a naturopathic physician. While most medical doctors are not familiar with his theory, D'Adamo said he's had a favorable response once they've read the book. After a quick review made at our request, Dr. Alex Reiner, a hematologist at the Puget Sound Blood Center, expressed interest.
"The theory and suggestion of dietary modifications is certainly intriguing and there very well might be some benefit there," Reiner said. "There certainly is a well-established association between particular blood types and an increased risk of certain diseases, such as ulcers."
Blood center researchers are studying possible links between blood types and other diseases such as diabetes, Reiner said, though he added that "further studies are required" to confirm a direct causal link between blood types, diet and disease.
D'Adamo lives and has a naturopathic medical practice in Greenwich, Conn., but did much of his research in University of Washington libraries while he was a student at Seattle's John Bastyr College in the early '80s. His conclusion, derived from anecdotal and scientific evidence, is that the answers to many of our diet and health woes are written in our blood.
Publishers went bananas over his manuscript. (Bananas, by the way, according to the blood-type diet, are highly beneficial for type B's and AB's, neutral for type O's. Type A's should avoid them; they interfere with their digestion.)
In the book, D'Adamo uses case studies as examples of how a host of ills - from high blood pressure to asthma and allergies, obesity to stomach ulcers - can be controlled through one of four diets corresponding to the four blood types: O, A, B or AB.
Which are you?
A quick survey around my desk revealed that more co-workers know their astrological sign than their blood type. (Try asking people; it's an amusing exercise.) Not so in Japan, where blood types often are exchanged in casual conversation and thought to reflect facets of one's personality, among other things, said D'Adamo. In Japan, he says, people routinely list their blood types on their Web pages.
D'Adamo, of Italian descent, is type A. He's a vegetarian, the proper diet for his blood type. He's healthy. This reporter, racially mixed, is type O. I'm an omnivore. And I must admit to a healthy skepticism about how my blood type could dictate what I eat.
"Everyone asks the same question: What does your blood type have to do with what you have in your diet?" D'Adamo said. "Is that any worse than the current assumption that everybody should eat the same? Entire books are written that say everyone should go to a high-fiber diet or everyone should be a vegetarian."
But why blood type? For one, it's loosely linked to your race. D'Adamo theorizes that blood types changed over generations as ancient populations migrated across continents, adapting to the food in their new locales.
Here's a brief lesson in blood-type history:
Western Europeans and many Japanese tend to be type A. Eastern Europeans, East Indians, northern Chinese, Koreans and a smaller portion of Japanese tend toward type B, as do Ashkenazic and Sephardic Jews. Type O, the oldest blood type, is approximately 50,000 years old and predominates among Africans and American Indians, but is also the most common, crossing many races and geographic regions. Type AB, the newest type, sprung up in Europe around A.D. 900, a consequence of mingling civilizations of people with type A and B blood.
The original O's were hunters and had acidic stomachs for digesting meat, says D'Adamo. Type A appeared between 25,000 and 15,000 B.C. as a mutation that proliferated because the change (a lower stomach-acid level) helped digest the grains and legumes of agrarian societies. He says Type B developed as populations traveled to the cooler Himalayan highlands between 10,000 and 15,000 B.C. and migrated east and west from there.
D'Adamo admits that even he was initially skeptical about the blood-type diet theory. His first inkling that "By Jove! Dad might be on to something" came when he discovered that type O's tend to get more ulcers. You remember, type O's are the ones with the acidic stomachs for digesting prime rib and Quarterpounders. Type A's, on the other hand, have a lower ulcer rate but a higher rate of stomach cancer, linked to low levels of stomach acid production. Eureka!
The difference, says D'Adamo, is largely in the lectins.
Each of the four blood types is distinguished by its chemical markers, or antigens. Your immune system uses your blood antigens to recognize foreign antigens in the bloodstream, such as from a virus. The blood antigens create antibodies that attach to the foreign antigens - a process called agglutination ("literally, gluing," D'Adamo says). This clump of antibody and foreign antigen is easier for the immune system to identify and destroy.
Blood types A and B also produce antibodies that reject each other's type. (Type AB does not; it can accept blood from any blood type. Type O, the universal donor, can give blood to any blood type but accepts only O.) According to D'Adamo, it turns out blood antigens do the same thing to certain foods, depending on the food and the blood type. Enter lectins.
Lectins are proteins found in foods. Certain lectin proteins are similar enough to one type of blood antigen to cause the antigens of another blood type to produce antibodies to attack and agglutinate, clumping the blood. D'Adamo contends that this blood clumping can contribute to a range of ills (irritable bowel syndrome in the intestines, cirrhosis of the liver), depending on the food protein and the blood type.
While the four blood-type diets were not designed for weight loss, D'Adamo has used them to help overweight people reach a more appropriate weight because, depending on the blood type, some foods will cause weight gain and others aid a slow metabolism. For example, while meat will tend to slow digestion and metabolism for type A, the type O stomach efficiently digests and metabolizes it. Conversely, carbohydrates can slow the type O metabolism.
Another example is a seaweed called bladder wrack. For type O, bladder wrack normalizes a slow metabolism, but does not have that effect on the metabolism of other blood types. The proper diet is just one component of maintaining an appropriate weight; D'Adamo also prescribes herbs and regular exercise, once again based on blood type. His research shows that while types O and B benefit from vigorous exercise, types A and AB do better with slower, more calming exercise such as yoga or brisk walking or swimming. Yoga is useful for all four types, but types O and B should combine it with more high-intensity exercise such as aerobics, martial arts, cycling or jogging.
At the back of the book, D'Adamo answers common questions such as: Why avoid foods that are the staple of your ethnic diet but do not fit your blood type? Do what you can, D'Adamo responds.
"You don't have to do this diet 100 percent," D'Adamo said. "It means learn what's right and know it. You'll do just fine."